| Miniproposals | ||||||||||
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| Operators | |
| Session leader(s): | Yuichi Takase |
| Physics operator(s): | Steve Golovato |
| Engineering operator(s): | Vinny Bertolino |
| Engineering Operator Run Comment |
| RF Coupling |
| Session Leader Plans |
| Physics Operators Plans |
| Session Leader Summaries |
| Entered: Jul 7 2004 03:49:08:773PM |
| Author: To Be Determined |
| Run Summary for 930917 ICRF coupling studies in D(H) plasma. Session Leader: Takase Physics Operator: Golovato Engineering Operator: Bertolino Objective of today's run was to obtain loading data as functions of 1) Plasma density 2) Plasma-antenna distance Deuterium ECDC was done overnight. We loaded 930916010 with gas puff programming from a previous deuterium run 930819. This was the first rf run after the break with almost no previous tuning or conditioning, and also only the second deuterium run on C-Mod. The limiter was at R=0.92m and the antenna at $=0.94m for most of the run. It took a while to obtain stable plasmas (there is a very narrow window between fizzles and runaway shots) and good rf tuning. Good tuning was obtained on shot 021. Thereafter, attempts were made to obtain a density ramp-up (Objective #1), but a controlled density rise was not obtained. Objective #2 was accomplished by shifting the plasma outward on shots 031 and 032, which resulted in increased loading. On shot 032 the limiter was moved back to R=0.93m. A scan of antenna position was not carried out because moving the antenna requires retuning, which will require several shots at present (in the future, we will keep a record of tuner positions for each antenna position so retuning can be accomplished in one shot). Disruptive activity was observed today when the rf power was stepped up to over 100 kW. Such reaction was not observed on 930819 up to a power level of 250 kW, and we believe this is caused by "de-conditioning" of the antenna which occurred during the shut down. We will need both vacuum and plasma conditioning to obtain higher powers needed for heating studies. |
| Physics Operator Summaries |
| Entered: Jul 7 2004 04:36:50:350PM |
| Author: To Be Determined |
| Physics Operator Summary - Run 930917 - Golovato ------------------------------------------------ Pre-run comments: Magnet cb and timing same as for shot 0916010. Gas fill from a-side pure D2. Puffing to start from a-side (pulse_gas_3). b-side-upper has 80/20 D2/H2 mixture (pulse_gas_2). ECDC all night in D2. 5 engr test shots preceeded plasma shots to look for problem in oh1. Problem did not appear, has been intermittant in past. Note: changes noted are for NEXT shot. shot # comment -------- --------- 6 shot 930916010 with gas programming from 930819026 (good D2 shot) fill 1.5e-5 dud 7 loaded shot 930916026 which had better breakdown setup moved pulsed gas to 15 ms later (-67ms to -52ms). gas arrived too soon last shot. null looked good on last shot. fizzled. fill too high, need 25% less for D2. 8 fill to 1.e-5. moved puff 15 ms later, gas still early. fizzled, got burst of hards. dropped oh2 v to -20 from 0 at ~5ms to help vertical stab during current ramp. moved efc turnon later (+10ms from -20ms). 9 serious runaway shot. moved puff 5ms earlier. raise fill to 1.1e-5. efc notched off (pid gains to 0) at 500ms, lets plasma go vertically unstable. this is now removed. 10 got a plasma. lowered initial puff level from 50 to 37. also lowered later puff a little. density ramping too also too much gas later in time. 11 only slightly more than a fizzle. lowered first puff more, also delayed second puff by about 5ms. current ramp faster than yesterday, raised oh1 early negative peak from -190 to -100 to increase bz ramp rate. limiter to 92 cm, antenna to 94. 12 good plasma. leave gas alone. work on removing late vertical disruption. reduced ef1u current to raise x-point later in shot. also raised oh2's sooner and more starting at 600 ms instead of 700ms to lower elongation later. finally changed z position from -3 to -2 cm. 13 OH2's moved in wrong direction. should disrupt earlier. disrupted before programming changes. lowered early gas and later gas puffs more. corrected oh2 programming. 14 runaway shot. very rapid current ramp. added back early gas puff, took away some of later puff. 15 another runaway shot. no late disruption, shot went to 1.2 sec, ended calmly. current ramp still too fast. moved gas programming earlier by ~4ms. also took out notch between puffs. have one long puff. 16 runaways again. moved gas 5 ms earlier, raised early puff and raised fill to 1.3e-5 from 1.1e-5. 17 fizzled, no runaways. notching efc for 10ms at 700ms. increasing gain on ip feedback from 2 to 4. moved gas timing later by 5 ms,but kept the levels the same. breakdown was late this shot. 18 fizzled. left gas timing the same, reduced length of initial puff. 19 good shot. no disruption, ended past 1 sec. some hards, add a puff between -10 and 0 to kill them off. 20 good again. added 500a to ef1l to divert plasma, reduce width of plasma, pull it off inner wall some. increased later gas to increase density. 21 ran into oh1 limit, didn't double swing. plasma elongated horizontally, r_centroid oscillated, then disrupted. rf now tuned pretty well. do density ramp, then move plasma radially to study loading. added some more late gas to ramp density. 22 good plasma. disrupted at 625ms where nl_04 goes above 6e19. maybe a density limti disruption. we'll lower the late gas a little to try to avoid it. later we can try to raise the current to increase the limit. 23 good, short, a some x-rays. tf crowbarred. disrupted again at same time. no efc this shot, probably tripped last shot. adjusted bz (oh1) during breakdown to keep plasma off inner wall. lowered late gas, added a gas blip at 560ms. 24 oh1 problem at zero crossing, long dead time around 360ms. plasma lost again when nl hits 6e19, at 530ms. moved gas blip to 400ms, lowered late gas. 25 some x-rays. no disruptions, clean end at 1+sec. trying something to fix oh1 problem but worked this shot. bz evolution diverging from trends of recent good shots. plasma scraping inner wall during startup because of high bz. may be cause of high zeff. adjusting oh1 to adjust bz again lowering current. nl flat at 4-4.5e19, blip not visible. increased blip to 40v for 20ms. 26 good shot. raised early gas to avoid runaways, raised blip to 60v for 5ms, density ramp barely visible. 27 x-rays, shorter plasma. killed by 400ms puff. reduced 400ms puff to 50v,3ms. moved early puff from -15ms to -20 ms. 28 fizzled. tf crowbar. lower puff at -20ms, lengthened it a little. balance between choking off breakdown and getting runaways. 29 fizzled. tf crowbar. loaded shot 26 to get early gas programming. added lower puff at 400ms. raised fill to 1.4e-5 from 1.3e-5. 30 fizzled. ramping r_cur from 67 to 69 and back down again from 400 to 600 ms. played with gas, lowering early gas, moving blip to 630ms. fill back to 1.3e-5. 31 good shot, some runaways. late puff kills plasma but r_cur excursion worked well. got rid of late puff, limiter moved out to 93cm, antenna only one cm behind. 32 runaways but good shot. shot ended at 615 ms. Post-run recap: duds 1 fizzles 8 serious runaway shot 4 good w/vert disrupt 3 good w/ps failure 3 good w/dens disrupt 4 good w/no disrupt 4 Totals - 14 good plasams, 13 runaway/fizzle/dud, 5 PS tests Post-run comments: Running with deuterium proved tricky, at least for me. Pre-breakdown gas programming is complicated and critical to getting good plasma. Current ramps were fast and Bz ramp had to be right also. See shots 14-20 where we got three runaway shots in a row, followed by two fizzles, then two 1+ sec plasmas. The window between fizzles and runaways was very small and even many "good" shots had non-negligible hards. Horne and I struggled with this the whole run. Ian provided the presciption to avoid the late vertical disruption that ended good shots at around 800 ms (see shots 12-13 with success on shot 19). Plasmas appeared to be dirty (high Zeff). This may have been due to hitting inner wall during startup (Bz ramp - Ip ramp problem) or the unconditioned antenna. The outboard limiter was run at 92cm without problems, even for the fairly "fat" plasmas we were running. I suggest we not move it out unless there is a compelling reason. We need to run it at 90.5cm for the two-strap antennas. The TF is now running at 4.8T. We need 5.3T for ICRF heating, so we should work on getting the TF up. This may affect breakdown and current ramp and may also require some adjustments of the alternator, so I'm told. |
| Session Leader Comments | |||
| Sep 17 1993 09:37:57:610AM | Yuichi Takase | RF coupling run in D(H).
Discharge cleaned overnight in D. Begin with 930916010. A-side plenum has D, B-side-upper has 20%H + 80%D mixture. Try to produce reproducible constant shots with rising density. Move the antenna/limiter, move the plasma, etc. | |
| Sep 17 1993 09:35:18:590AM | 930917006 | Yuichi Takase | Shot 006
Shots 1-5 were power tests. First attempt at plasma on shot 006. No plasma. |
| Sep 17 1993 09:53:54:770AM | 930917007 | Yuichi Takase | Fizzle.
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| Sep 17 1993 10:09:45:060AM | 930917008 | Yuichi Takase | Early disruption.
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| Sep 17 1993 10:54:00:470AM | 930917009 | Yuichi Takase | Shot 009
Runaway shot. Great tune! R_lim=95, R_ant=97. ST=360, PS=624. |
| Sep 17 1993 10:54:41:560AM | 930917010 | Yuichi Takase | Shot 010
Disrupted @ .2sec. |
| Sep 17 1993 10:59:01:140AM | 930917011 | Yuichi Takase | Shot 011
R_lim=92, R_ant=94. Disrupted very early (40msec). |
| Sep 17 1993 11:27:26:980AM | 930917012 | Yuichi Takase | Shot 012
R_lim=92, R_ant=94. Good shot, 470 kA, .8sec. P_rf=40kW (peak). |
| Sep 17 1993 11:38:49:210AM | 930917013 | Yuichi Takase | Shot 013
R_lim=92, R_ant=94. Disrupt at .35sec. |
| Sep 17 1993 11:58:00:130AM | 930917014 | Yuichi Takase | Shot 014
R_lim=92, R_ant=94. Not a good-looking plasma. Bad tune. |
| Sep 17 1993 12:12:02:310PM | 930917015 | Yuichi Takase | Shot 015
R_lim=92, R_ant=94. A long shot (over 1sec), low density, nonthermal. |
| Sep 17 1993 12:23:08:910PM | 930917016 | Yuichi Takase | Shot 016
R_lim=92, R_ant=94. A long shot (over 1sec), low density, nonthermal. |
| Sep 17 1993 12:30:52:860PM | 930917017 | Yuichi Takase | Shot 017
R_lim=92, R_ant=94. Fizzle. |
| Sep 17 1993 12:51:05:270PM | 930917018 | Yuichi Takase | Shot 018
R_lim=92, R_ant=94. Fizzle. |
| Sep 17 1993 01:08:59:070PM | 930917019 | Yuichi Takase | Shot 019
R_lim=92, R_ant=94. Good shot, rising density. Still working on tuning. |
| Sep 17 1993 01:32:44:550PM | 930917020 | Yuichi Takase | Shot 020
R_lim=92, R_ant=94. Good shot, steady density. Still working on tuning. |
| Sep 17 1993 02:03:41:170PM | 930917021 | Yuichi Takase | Shot 021
R_lim=92, R_ant=94. Unstable plasma (and falling current), acceptable tuning. |
| Sep 17 1993 02:28:52:640PM | 930917022 | Yuichi Takase | Shot 022
R_lim=92, R_ant=94. Disrupted at 0.6sec, shortly after rf power step-up. |
| Sep 17 1993 02:29:29:910PM | 930917023 | Yuichi Takase | Shot 023
R_lim=92, R_ant=94. Disrupted at 0.6sec, shortly after rf power step-up. Reduce rf power for the next shot. |
| Sep 17 1993 02:52:07:260PM | 930917024 | Yuichi Takase | Shot 024
R_lim=92, R_ant=94. Ugly disruptive shot. |
| Sep 17 1993 03:14:51:020PM | 930917025 | Yuichi Takase | Shot 025
R_lim=92, R_ant=94. Good shot, steady density @ 4e19 (nel04). P_rf=40kW. |
| Sep 17 1993 03:32:58:500PM | 930917026 | Yuichi Takase | Shot 026
R_lim=92, R_ant=94. Good shot, slightly rising density @ 4e19 (nel04). P_rf=60kW, good tuning. |
| Sep 17 1993 03:54:09:270PM | 930917027 | Yuichi Takase | Shot 027
R_lim=92, R_ant=94. Disruptive after 0.4sec, too much gas puff. P_rf=80kW. |
| Sep 17 1993 04:18:35:150PM | 930917028 | Yuichi Takase | Shot 028
R_lim=92, R_ant=94. Fizzle. |
| Sep 17 1993 04:18:48:500PM | 930917029 | Yuichi Takase | Shot 029
R_lim=92, R_ant=94. Fizzle. |
| Sep 17 1993 04:55:00:580PM | 930917030 | Yuichi Takase | Shot 030
R_lim=92, R_ant=94. Fizzle. |
| Sep 17 1993 04:56:23:850PM | 930917031 | Yuichi Takase | Shot 031
R_lim=92, R_ant=94. Good shot, disrupt at the end after rf power step-up. R_cur ramp worked. Edge density and loading goes up with r_out shift. |
| Sep 17 1993 05:37:51:760PM | 930917032 | Yuichi Takase | Shot 032
R_lim=93, R_ant=94. Good shot, disrupt at 0.6sec R_cur ramp worked, but not as clean as 031. |
| Physics Operator Comments |
| Engineering Operator Comments | ||||
| Shot | Time | Type | Status | Comment |
| 1 | 08:10:16:040AM | Test | Ok | oh1 test |
| 2 | 08:20:38:440AM | Test | Ok | oh1 test |
| 3 | 08:29:59:030AM | Test | Ok | oh1 test pulse good |
| 4 | 08:38:02:290AM | Test | Ok | oh1 test |
| 5 | 08:47:15:090AM | Test | Ok | oh1 test ok |
| 6 | 09:25:09:070AM | Plasma | Ok | no faults |
| 7 | 09:49:01:390AM | Plasma | Ok | oh1 >1scr not conducting |
| 8 | 10:01:39:330AM | Plasma | Ok | no faults |
| 9 | 10:14:42:060AM | Plasma | Bad | tf auto crobar fired after flattop |
| 10 | 10:34:00:800AM | Plasma | Ok | oh1 >1scr not conducting late in shot |
| 11 | 10:53:59:310AM | Plasma | Ok | no faults |
| 12 | 11:09:31:310AM | Plasma | Ok | no faults |
| 13 | 11:28:35:200AM | Plasma | Ok | no faults |
| 14 | 11:43:01:700AM | Plasma | Ok | no faults |
| 15 | 11:56:21:280AM | Plasma | Ok | no faults, plasma >1sec!!!!!!!!!!! |
| 16 | 12:10:44:390PM | Plasma | Ok | no faults |
| 17 | 12:25:34:370PM | Plasma | Ok | no faults |
| 18 | 12:40:46:980PM | Plasma | Ok | no faults |
| 19 | 12:58:49:190PM | Plasma | Ok | no faults |
| 20 | 01:13:59:920PM | Plasma | Ok | no faults |
| 21 | 01:28:39:670PM | Plasma | Ok | oh1 did not go negative |
| 22 | 02:02:42:550PM | Plasma | Ok | no faults |
| 23 | 02:17:53:490PM | Plasma | Ok | tf auto cbar fired late in the shot |
| 24 | 02:44:06:430PM | Plasma | Bad | oh1 hesitated crossing zero |
| 25 | 03:03:39:220PM | Plasma | Ok | no faults |
| 26 | 03:18:43:130PM | Plasma | Ok | no faults |
| 27 | 03:36:17:240PM | Plasma | Ok | no faults |
| 28 | 03:50:34:710PM | Plasma | Ok | tf auto cbar fired -- all breakers pulled late in the shot |
| 29 | 04:08:41:250PM | Plasma | Ok | tf auto cbar late in the shot |
| 30 | 04:24:47:640PM | Plasma | Ok | no faults |
| 31 | 04:37:52:980PM | Plasma | Ok | no faults |
| 32 | 04:55:41:030PM | Plasma | Ok | no faults |